In the past, inexpensive wooden articles, such as disposable shipping pallets, have been manufactured with the use of a gang saw capable of cutting four to eight slats for the upper surface of the wooden shipping pallet on each pass of the lumber through the gang saw. Because they permit a plurality of pallet slats to be cut simultaneously during each pass, gang saws permit a reduction in the labor required in cutting lumber for the pallet.
The reduction of labor obtained through the use of a gang saw is not without its price, however. Gang saws are expensive and require substantial electric power to drive the multiple saw blades. The high peak electrical demand required in starting the large motors needed to drive the multiple blades of the gang saw requires the payment of peak-demand penalties for electric power; and the high power demand of such motors requires that the plant facilities be wired with 440 three-phase service and other uncommon electrical services necessitated by such high-power equipment.
Furthermore, gang saws are wasteful of lumber. The gang-saw blades typically produce a kerf on the order of 0.200 to 0.250 inch, turning as much as thirty percent of the lumber being cut into sawdust. This wasteful production of large quantities of sawdust presents significant waste disposal and fire safety problems. In addition, where irregularities in the wood, such as knots, voids, and splits, occur, the gang saw will frequently break the boards being cut which is also a significant waste. The high initial cost and high operating cost have prevented the use of gang saws by many small manufacturers.
Band saws are desirable wood-cutting means. They are not wasteful of wood because their teeth produce only a small kerf, for example, 0.030 to 0.050 inch, resulting in an extremely small portion of the wood being wasted as sawdust. As set forth above, the production of sawdust by sawmills is a significant problem because of the loss of potential processed lumber, the difficulty and cost of disposal, and the danger of spontaneous combustion of the sawdust.
The advantages of using a band saw to manufacture such items as disposable, wooden, shipping pallets are significant; however, band-saw apparatus have not been used in such manufacturing operations because it was necessary to handle the wood being cut manually, resulting in slow operation and high labor costs. Prior systems for automatically feeding lumber through a band saw generally included a work guide mounted with relation to the plane of the saw blade to permit adjustment of the thickness of the cuts, and an opposed plurality of driven wheels, which also had to be adjustably mounted with respect to the plane of the saw blade to permit variable thicknesses of lumber to be cut. In operation, a piece of lumber would be placed between the driven wheels and the guide and driven through the band saw to cut the lumber into the prescribed thickness. Upon completion of the cut, the uncut work was carried by hand back to a "home" position and again fitted into the drive means in preparation for the next cut. Reciprocation of the uncut lumber was not possible with prior band-saw apparatus because during the return stroke of the work after completion of the cut, the work would contact and rub against the band-saw blade and often damage the blade or pull it off of its driving wheels. Band-saw blades with teeth on both edges capable of cutting the lumber both during the forward and return movement of the lumber were also not entirely acceptable because of the size and cost of the blades.
In addition to the necessity of carrying the uncut lumber back to the home position following each cut, it was also necessary, when using band saws, to position a new piece of lumber to be cut into the apparatus after the piece being operated on had been fully cut. In addition, the apparatus had to be carefully monitored to insure that the workpiece was properly aligned and positioned relative to the cutting plane of the blade to obtain straight, uniform slats of the desired thickness. Also, in prior systems, to adjust the tension of the saw blade or to replace a saw blade was a relatively complicated and time-consuming project, requiring that the system be shut down for substantial periods.
Thus, in general, the use of prior band-saw systems to cut a plurality of pieces of wood required substantial operator involvement to operate and monitor the system. This resulted in substantial labor costs and a relatively slow operating speed.